This invention relates to mobile storage systems, and in particular to mobile storage systems having sensors to prevent the closure of an aisle between two storage units when an obstacle is present in the aisle, without the need for physical contact with the obstacle.
Mobile storage systems are widely used and well known to comprise a series of storage units which have shelves or bins, for example. Except for one or both of the end units, which may be stationary, each of the storage units will normally be movable, such as on rails, to create an access aisle between two of the units. As this aisle opens, the other units are positioned in close side-by-side relationship to minimize the overall floor space required for the units, moving together to do so. Especially in larger mobile storage units and systems, the carriages can be quite large, and the loads they carry quite heavy, such as steel or construction materials. It is commonly necessary, therefore, to provide motorized means for moving the units. These motorized moving means in turn require the use of means for preventing adjacent units from moving together when an obstacle, such as a person, is positioned between them, so as to avoid injury or damage.
In the past it has been customary to provide a sweep or safety switch bar for notifying the control system to inhibit motion of a storage unit if the bar encounters, while moving to close the aisle, an obstacle or impediment to movement, as shown for instance in U.S. Pat. Nos. 4,743,078 and 4,733,923. When such a structure is used alone to protect a person, however, the requirement of physical contact with the bar can be disconcerting and startling, which can make use of this structure alone undesirable. Use of a photoelectric sweep, as disclosed in U.S. Pat. No. 5,121,975, is only slightly less disconcerting, as the moving storage unit must still move quite close to a person before its motion is interrupted.
Another alternative is to use a "safety floor" such as set forth in U.S. Pat. Nos 4,744,307 and 4,693,184, which disclose constructions of floor panels including safety switches. The weight of a person or other obstacle on one of the floor panels activates one of the safety switches, which notifies the control system to inhibit movement of the storage units. While these units work very well from a safety standpoint, they can be rather expensive, resulting in their non-use in certain situations. And U.S. Pat. No. 4,745,516 even discloses the use of a safety sweep and a safety floor in combination. Even this combination, however, may not properly sense that an obstacle remains in the aisle even though no switches are closed, such as on occasion may occur when a very light obstacle is in the aisle, or when a person needs to reach an item on a high shelf and may step onto a lower shelf to reach the item.
This invention relates to improvements to the structure set forth above, and to solutions to some of the problems raised or not solved thereby.